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More computers than pots

So I'm having a bit of apartment woes lately. The third out of four elements on glass ceramic cooking hob failed so I notified the landlord. Since this part of Slovenia has mild winters and Italian mentality, contractors say they will "call you" and then nothing happens for a week or maybe three months. It's one of reasons I have a job here because locals are not as competent. Knowing that I proposed to order new hob online and get a receipt. I picked 2x induction + 2x ceramics as it's most compatible with future tenants and the people here make espresso in caffettiera and the most popular one is made of aluminium.

The landlord is some sort of professor at faculty of electronics and he read the specs of my proposed hob and proposed max 3kW as 6kW (pretty much all standard electric, glass ceramic or induction hobs are ~2kW per element and 6kW total) would mean 20amps. Then he started talking about me paying for changing to 3phase.

Obviously in contract and in general law it's on the landlord to do major repairs.

So since this is going to take weeks I ordered 50 Euro single element induction hob online, so that I have at least two elements. Lately I've been cooking more and I strive to precook lunch for next work day at least 3-times a week, which requires two elements. Since the store notified me it's available for pickup a day early and since I had a time window between work and freelance to fight the rush hour traffic (15km/h 10mph average speed) I got it today. Brought it home and decided to test my cookware collection consisting of two pans left by former flatmate some years ago and three pots, one enamel probably as old as me, one on permanent loan from parents and the third bought cheaply in Ikea. The reason I have so few is the thinking I'll buy really good cookware one day and I'll make do with what I have. So all three pots work with induction but the pans don't. I'm thinking of buying used AMC or somesuch.

Having performed the inventory of my cookware I realized I have more working computers and about as many camera lens as pots.

We have ELO pots, especially bought for induction; and they work very well.
One thing: the pot can make a huge difference. We tested with an older Gerlach and a new ELO of same size with the same amount of water on the same induction cooking plate. On the same setting, the water in the ELO boiled one minute faster. So over time that adds up!

pixarDream as if you'll live forever. Live as if you'll die tomorrow. (James Dean)

Although I suspect this has to do with transformation efficiency in terms of time. I assume the difference in energy used is very small (basically, the energy lost to the environment in the additional minute). Apparantly, some pots use more Watt then others?

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[...]the pervading principle and abiding test of good breeding is the requirement of a substantial and patent waste of time. - Veblen

1 minute of time at 25€/h is 41 cents. At most expensive tariff with VAT 1kWH is 10 cents. So even if you save 1kW (doubtful - at half of peak efficiency) power for 20 minutes, it's still 3 cents. The time saving is more important.

Although I suspect this has to do with transformation efficiency in terms of time. I assume the difference in energy used is very small (basically, the energy lost to the environment in the additional minute). Apparantly, some pots use more Watt then others?

It is actually something I was looking for but could not find... Does the fact that it takes longer (due to the pot) mean that it uses more power? The power setting on the cooking plate is the same, does it translate to the power consumed? And also: which would be the more efficient way to heat water: an electric kettle or a (decently suitable) kettle on an indution plate?

pixarDream as if you'll live forever. Live as if you'll die tomorrow. (James Dean)

We have a set of non-stick T-Fal and oven glassware (Corning), but do most of our cooking in high quality cast iron cookware. This includes Dutch ovens, stovetop grills and bakeware. Well seasoned and maintained, there's nothing better.

It is actually something I was looking for but could not find... Does the fact that it takes longer (due to the pot) mean that it uses more power? The power setting on the cooking plate is the same, does it translate to the power consumed? And also: which would be the more efficient way to heat water: an electric kettle or a (decently suitable) kettle on an indution plate?

It seems to me that due to the law of the preservation of energy, the amount of energy used to boil water is independent of the time it takes to get the water boiling provided that there is no loss in the system. Obviously there is in normal circumstances as water that is warmer than its suroundings will dissipate heat and if it takes longer to get to boil it will dissipate for a longer time. But in terms of W, a slower boiling pot will consume a lower W but for a longer time (and given the losses it will consume more Wh).

A funny illustration is where lights on a bike are powered by a dynamo. You can actually feel it is harder to bike. Detach the cables and, even though the dynamo is still driven by the wheel, it is way easier to bike. You just put in the heat generated by friction but it is noticable that you do not provide power to the lights.

Edit: The setting on the cooking plate regulates the power it *can* give at a setting. The receiver of that power is then determines how much is taken (if impedance of receiver is zero, then it is fully set by the setting on the cooking plate). A lot like the volume knob on an amp.

Last edited by Umfriend; 7th December 2018 at 16:49.

Join MURCs Distributed Computing effort for Rosetta@Home and help fight Alzheimers, Cancer, Mad Cow disease and rising oil prices.
[...]the pervading principle and abiding test of good breeding is the requirement of a substantial and patent waste of time. - Veblen

It seems to me that due to the law of the preservation of energy, the amount of energy used to boil water is independent of the time it takes to get the water boiling provided that there is no loss in the system. Obviously there is in normal circumstances as water that is warmer than its suroundings will dissipate heat and if it takes longer to get to boil it will dissipate for a longer time. But in terms of W, a slower boiling pot will consume a lower W but for a longer time (and given the losses it will consume more Wh).

Yes, obviously... But the point is: why is one pot slower than another pot using the same power setting? Is it 1) because it takes the same amount of power but suffers more losses in transferring the heat to the water, or 2) because it can take less power. (or a combination) In case 1, your slower cooking pot would take the same amount of power over a longer time; in case 2 it would take less power but during a longer time.

Originally Posted by Umfriend

Edit: The setting on the cooking plate regulates the power it *can* give at a setting. The receiver of that power is then determines how much is taken (if impedance of receiver is zero, then it is fully set by the setting on the cooking plate). A lot like the volume knob on an amp.

Not sure I get this one...

pixarDream as if you'll live forever. Live as if you'll die tomorrow. (James Dean)

Well, the edit actually is more or less the same as your #2, it can take less power.

But come to think of it, it could be that one pot itself losses more heat to the environment than the other. Not sure *how*, as it would have to be hotter than the other I'd think but maybe there is a pot that is better insultated on the outside than the other. Personally, never heard of pots being isolated in any way though. Unless if one has metal handels and the other has plastic for instance, that might make a bit of a difference.

Do you have specific model numbers for the pots?

Join MURCs Distributed Computing effort for Rosetta@Home and help fight Alzheimers, Cancer, Mad Cow disease and rising oil prices.
[...]the pervading principle and abiding test of good breeding is the requirement of a substantial and patent waste of time. - Veblen

A pot is basically a heatsink transferring energy from cook element to food and to air. Heat is transferred by:
heat flow
thermal radiation
convection (this is why you get better results if you cover the pot)

Like materials in heatsink differ in terms of heat transfer (aluminium being better than copper with heat flow) so do materials in pots. Different steels, different surface treatment all probably influence heat flow.

Update on the saga 14 days after notifying the landlord:
- he said electrician will come to assess cabling a week ago.
- last week I called electrician who said he'll call me monday.
- on Monday he said he is ill

I ordered used AMC induction capable pan on ebay.
AMC is good - my parents are using a set for 30 years and it's still in great condition. The secuquick is expensive and they never used it as well as some other dishes. So my plan is to slowly buy just the cookware I need over time, possibly used.

My mother has AMC for as long as I can remember, and they are very good. The lifetime warranty also works; she had a handle-isolation replaced for free after 20-or so years!
If you need an anti-stick pan, I can really recommend Lacor. They work well on induction, and nothing sticks. You can crack an egg in it (hot ot cold), fry it and it just comes off (healthy as well: not much fat needed).

pixarDream as if you'll live forever. Live as if you'll die tomorrow. (James Dean)

My AMC induction pan from ebay arrived on saturday in nearly mint condition. Parents gave me one compatible cover from their set.

And I gave the landlord a deadline (worded in very polite cordial tone - I learned this from my lawyer) so he paid for the new stovetop. I picked it up at post office today and though today is Christmas eve, techie from Ljubljana is arriving to install it at 15:30. (Reponse times like that are completely unthinkable in this part of Slovenia).

VJ to answer your question why does one work better... Induction works using a magnetic field which causes a high amount of eddy currents within the ferrous materal of the pot or pan. Cast Iron works best, alloys with less ferrous material will not create as strong of eddy currents and thus less heating. Another aspect to this is the thickness of the ferrous material, thicker the better if you want Induction (eddy current) for heating.

Conversely, transformers use special magnetic steel that is forged with a current flow through it aligning the crystalline structure as it solidifies. This is then pressed into thin sheets and laminated to create the core. The thin plates prevent the creation of eddy currents because we don't want glowing hot transformers

So amount of ferrous material and thickness of ferrous material, with well seasoned cast iron being best

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